In T 702/99 the board made extensive remarks with regard to the probative value of test evidence. It noted that it was essential that comparative tests conducted by a number of persons as evidence for or against qualities such as an improved "feel" of a product (e.g. cosmetics) be made under conditions of maximum objectivity on the part of those conducting the tests. Since such evidence was opinion evidence and thus inherently subjective, its value lay in the number of similar or same opinions and the tribunal faced with such evidence will seek to judge the objective value of a number of subjective opinions. Parties to proceedings should adopt the same standards in the preparation of such test evidence as they should in the preparation of experimental evidence. While the use of independent persons would naturally tend to carry more weight, the use of employees might not be objectionable per se as long as the test conditions were designed to ensure that the employees were not biased by prior knowledge of either the tested products or of their employer’s expectation of the test result. The presentation of test evidence also had to be accurate, but the format of the presentation was of secondary importance; a carefully prepared report and/or table might convey as much information as a large number of statements from the testers.
In T 453/04 the board found the experimental evidence advanced by the appellant (opponent) to be defective for two reasons. Firstly, the teachings of the patent in suit were not accurately replicated. Secondly, the product presented as representative of the prior art had not been shown to belong to the prior art. Thus the experimental evidence of the appellant did not demonstrate that the process steps set out in claim 1 of the main request resulted in products indistinguishable from those of the prior art.